Question 4(iii)
If a light of a single colour is passed through a liquid having a piece of glass suspended in it, so on changing the temperature of the liquid, at a particular temperature, the glass piece is not seen.
(a) At what situation, the glass piece will not be seen?
(b) Why the light of a single colour is used?
(c) How can you define the term refractive index of a medium? State whether it can be less than 1 or not.
(a) The glass piece is not seen when the refractive index of the liquid becomes equal to the refractive index of glass.
(b) The light of a single colour is used as the refractive index of a medium (glass or liquid) is different for the light of different colours.
(c) The refractive index of a medium is defined as the ratio of the speed of light in vacuum (or air) to the speed of light in that medium.
The refractive index of a transparent medium is always greater than 1 (it cannot be less than 1) because the speed of light in any medium is always less than that in vacuum ( i.e. V < c ) and μ = 1 for air or vacuum.